Regenerative heat recovery unit comprising heat accumulators tiltably movable to have a valve function

ABSTRACT

A heat recovery unit comprising a case (1), which encloses at least one regenerative heat accumulator (5), whereby the casing (1) has a supply air opening (10), an exhaust air opening (15), an exterior air opening (20) and a under-air opening (25), and whereby exhaust air and supply air alternately pass through the heat accumulator (5). The heat accumulator (5) has, via a rotational movement, a valve function which opens and respectively closes the openings (10-25) when the heat accumulator (5) rotates from a first position for exhaust air throughflow to a second position for exterior air throughflow.

FIELD OF THE INVENTION

The present invention relates to a heat recovery unit comprising acasing which contains at least one regenerative heat accumulator,whereby the casing has an inlet air opening, an exhaust air opening, anexterior air opening and a used-air opening, and whereby the exhaust airand the exterior air alternately pass through the heat accumulator.

BACKGROUND OF THE INVENTION

Heat recovery units are used in, amongst others, ventilation systems fore.g. ventilating buildings and at the same time returning the heat outof the exhaust air which is ventilated out from the building to theexterior air which is fed into the building in the form of inlet air.

A heat recovery assembly which is present on the market, has two platehousings which each surround their own regenerative plate package whichforms the heat accumulators. Each plate housing is mutually joined withtwo valve housings. Each valve housing comprises a valve leaf which areeach influenced by their own valve motor. One of the valve housings isequipped with a supply air fan which is connected to a supply airchannel on the valve housing, and with an exhaust air fan which isconnected to an exhaust channel on the valve housing. The valve housingitself is connected to each and all of the plate housings via a supplyair opening resp. an exhaust air opening on the respective platehousings. The second valve housing is equipped with a used-air channeland an exterior air channel and is connected to each of the platehousings via a used-air opening resp. an exterior air opening of therespective plate housings.

Exhaust air resp. exterior air passes alternately through the platepackages. When one of the plate packages has warmed up and the other hascooled, the valve leaves in the valve housings are switched over,whereby the exhaust resp. exterior air changes plate package and havethe opposite direction of flow compared with the air which previouslyflowed in the respective plate packages.

Another existing heat recovery assembly is the rotation heat exchangerwhere a continuous airflow flows through a rotating cylinder. The axisof rotation of the cylinder extends into a plane which coincides with awall. On one side of the wall, warm air flows and on the other side coldair flows. By letting the warm air pass through the cylinder, the partof the cylinder which is on the "warm" side is warmed up. When thecylinder rotates, the warmed up part of the cylinder will go over to the"cold" side, whereby the cold air which flows through the cylinder iswarmed up.

OBJECTS OF THE INVENTION

The main object of the present invention is to achieve a heat recoveryunit which is equipped with at least one regenerative heat accumulator,which eliminates the need of a separate cross-over valve, which controlsthe exhaust air and the exterior air which pass through the heataccumulators. Preferably two heat accumulators are coupled together to aheat recovery unit.

Another object of the present invention is to provide a heat recoveryunit which has a very low sound change in the ventilation system whenthe switching over occurs from the exterior air to the exhaust air, andvice versa, in the heat accumulators.

A further object of the present invention is to provide possibility ofrecirculatory operation with the heat recovery unit, which recirculatesthe exhaust air through the supply air opening under special operatingconditions.

A further object of the present invention is to provide that the airflows in the same direction through the openings in the casing,irrespective of the direction of the air through the heat accumulators.

A further object of the present invention is to provide a low pressuredrop across the heat recovery unit.

A further object of the present invention is to provide a high degree oftemperature exchange in the heat recovery unit.

A further objector of the present invention is to provide a heatrecovery unit which permits simple cleaning.

SUMMARY OF THE INVENTION

According to the invention these objects are achieved by a heat recoveryunit in which the heat accumulator, by means of a rotating movement, hasa valve function which opens resp. closes said openings when the heataccumulator moves from a first position for exhaust air throughflow to asecond position for exterior air throughflow.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail below by means ofexamples of embodiments with reference to the appended drawings.

FIG. 1 shows a perspective view of a heat recovery unit according to afirst embodiment.

FIG. 2 shows a view from above of two heat recovery units which arecoupled together to form a heat recovery assembly.

FIG. 3 shows a perspective view of a heat recovery unit according to asecond embodiment.

FIG. 4 shows a side view of a heat recovery unit according to the secondembodiment.

FIG. 5 shows an example of the application of heat recovery unitaccording to the second embodiment.

FIG. 6 shows a side view of a heat recovery unit according to the secondembodiment in a third position.

FIGS. 7-8 show side views of a heat recovery unit according to a thirdembodiment in two different positions.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a perspective view of a heat recovery unit according to afirst embodiment. The heat recovery unit comprises a casing 1 whichforms a space 2, which contains a regenerative heat accumulator 5.According to this embodiment the casing 1 is elongated with a lengthwhich is greater than its width and height. The heat accumulator 5 whichis placed inside the casing 1 has a length and a width which aresomewhat less than the length and width of the space 2 which is formedby the casing 1 so that a clearance is formed between the inner surfaceof the casing 1 and the heat accumulator 5. The thickness of the heataccumulator 5 is less than the height of the space 2. This allows theheat accumulator 5 to rotate forwards and backwards inside the casing 1.The swinging movement takes place as a tipping movement around a shaft30 which carries the heat accumulator 5. The shaft 30 passes through ahole in the casing 1 and is mounted in bearings in the casing 1 on bothsides of the heat accumulator 5. In FIG. 1 the shaft 30 is imagined tobe horizontal.

The casing 1 has ends at which a supply air opening 10, an exhaust airopening 15, an exterior air opening 20 and a used-air opening 25 arearranged, which each cooperate with end faces 35 of the heat accumulator5. The end faces 35 are preferably parallel with the shaft 30 and planarand lie against the inside of the inner surfaces of the casing 1 aroundthe openings 10-25. The supply air opening 10 and the used-air opening25 resp. the exhaust air opening 15 and the exterior air opening 20 areseparated by means of a wall part 27 resp. 28, which can be formed bypart of the casing 1. In the embodiment shown, both of the end faces 35have sealing strips 36 along their upper and lower edges. In a firstposition, shown in FIG. 1, the upper strip 36 of the lefthand end face35 seals against the upper side of the casing 1, and the lower stripagainst the lower edge of the wall part 28, at the same time as theupper strip 36 of the righthand end face 35 seals against the upper edgeof the wall part 27 and its lower strip seals against the inside of thebottom of the casing 1.

The heat accumulator can be built up from a number of plates 37 (FIG. 4)which forms a plurality of throughflow channels 38 for air. Thethroughflow channels 38 are preferably directed in the direction of thethickness of the heat accumulator 5. The plates 37 consequently form alarge heat-absorbing resp. heat-emitting surface.

The heat recovery unit can be used in a ventilation system forventilating a building, e.g. an apartment house or an office building.The air which leaves rooms in the building by the ventilation is calledexhaust air and the air which is supplied to the rooms is called supplyair.

By means of its forwards and backwards rotating movement the heataccumulator has a valve function which opens resp. closes said openings10-25 when the heat accumulator 5 rotates from a first position forexhaust air throughflow to a second position for supply air throughflow.

With exhaust air throughflow, when the heat accumulator 5 is positionedin the first position, exhaust air at room temperature flows in throughthe exhaust air opening 15 and into the space 2 in which the heataccumulator 5 is positioned. The exhaust air room temperature flowssubsequently through the heat accumulator 5 in a direction whichsubstantially corresponds to the direction of its thickness. The heataccumulator 5 is thereby heated up by the throughflowing exhaust air.The exhaust air then flows out through the used-air opening 25 in theform of used air and subsequently leaves the space 2 in which the heataccumulator 5 is placed. The used air which leaves the used-air opening25 can subsequently suitably flow into a channel 82 (FIG. 5), whichtransports the used air out of the building.

A first sensor 55 senses the temperature of the used air which leavesthe used-air opening 25. A reference sensor 56 can, for example, beplaced in the building which is to be ventilated, whereby the referencetemperature will correspond to the room temperature in the building. Thefirst sensor 55 and the reference sensor 56 are connected to a controlunit 60. When the difference between the temperature which the firstsensor 55 senses and the temperature which the second sensor 56 sensesdecreases to a predetermined value, the control unit 60 gives a signalto a stepping motor 62, which is connected to the shaft 30, whereby themotor 62 rotates the heat accumulator 5 to the second position forsupply air throughflow. Instead of a stepping motor it is conceivable touse another power generating means such as a hydraulic or pneumaticcylinder.

During exterior air throughflow, exterior air flows in through theexterior air opening 20 and into the space 2 in which the heataccumulator 5 is positioned. The exterior air then flows through theheat accumulator 5 in a direction which substantially corresponds to thedirection of its thickness. The exterior air is thereby heated up by theheat accumulator 5 warmed up by the exhaust air. The air then flows outthrough the supply air opening 10 in the form of supply air andconsequently leaves the space 2 in which the heat accumulator 5 ispositioned. The supply air which leaves the supply air opening 10 thenflows either directly into the building or into a duct system (notshown) which distributes the air into the different rooms of thebuilding.

A second sensor 57, which is placed by the supply air opening 10 andconnected to the control unit 60 senses the temperature of the warmed upsupply air. When the difference between the temperature which the secondsensor 57 senses and the temperature which the reference sensor 56senses increases to a predetermined value, the control unit 60 gives asignal to the stepping motor 62, whereby the motor 62 tips the heataccumulator 5 to the first position for exhaust air throughflow.

A fan part 65 which comprises two fans 66,67 (FIG. 4) can be connectedto the supply air opening 10 and the used-air opening 25, and a filterpart 70 which comprises two filters 71,72 can be connected to theexhaust air opening 15 and the exterior air opening 10.

When the heat accumulator 5 is heated up by the exhaust air throughflow,the exhaust air at room temperature will first meet one side, in FIG. 4the lower side, of the heat accumulator 5. This first side of the heataccumulator 5 will have a higher temperature than the second side, ifthe heat accumulator 5 is rotated to the second position before thesecond side of the heat accumulator 5 has been able to achieve the sametemperature as the first side.

According to the first embodiment in FIG. 1, the exhaust air and thesupply air flow in opposite directions through the heat accumulator 5.This means that the exterior air first will meet the side of the heataccumulator 5 which has the lowest temperature. The exterior air willconsequently be successively warmed up along its flow path through theheat accumulator 5, which increases the total efficiency of the heatrecovery unit.

FIG. 2 shows a view from above of two heat recovery units according toFIG. 1, which are connected to form a heat recovery assembly. Theexterior air openings 20 on each unit are coupled together by a tube 31,the exhaust air openings 15 are coupled together by a tube 31 (notshown), the used-air openings 25 are coupled together by a tube 32 andthe supply air openings 10 are coupled together by a tube 32 (notshown). The tube 31, which is connected to the exterior air opening 20,discharges into an exterior air channel 33 in which a filter 71 isarranged. The tube 31, which is connected to the exhaust air openings 15discharges in an exhaust air channel 33, in which a filter 72 isarranged (not shown). The tube 32 which is connected to the used-airopenings 25 discharges into a common used-air channel 34, in which a fan66 is arranged. The tube 32 which is connected to the supply airopenings 10 discharges into a common supply air channel 34, in which afan 67 is arranged (not shown).

The rotational movement of the heat accumulators 5 are so controlledthat when the heat accumulator 5 of one of the heat recovery units is inthe first position for exhaust air throughflow, the heat accumulator 5of the second heat recovery unit is in the second position for exteriorair throughflow, and vice versa.

In this way the ventilation in for example a building can be increasedcompared with only one heat recovery unit, whereby a nearly continuousventilation of the building is achieved. Each of the heat recovery unitscan be equipped with its own stepping motor 62 which brings about therotationary movement of the respective heat accumulator 5. In this casethe motors 62 should be synchronized so that when one of the heataccumulators 5 is in the first position, the second heat accumulator 5should be in the second position. This synchronization can be performedwith a control means 75. Alternately, the heat recovery assembly can beequipped with only one motor, whereby the rotational movement of themotor is transferred to each of the shafts 30 on the heat accumulators 5by a gear or a link mechanism (not shown).

Each of the heat recovery units can be equipped with sensors 55-57 whichsense the temperature as described above in connection with FIG. 1.However, it is also appropriate that common sensors 55-57 and a singlecontrol unit 60 are arranged for both of the heat recovery units inorder to give control signals to the electric motors 62 or the electricmotor. The control unit 60 can be connected to the control means.

It is also possible to couple together more than two heat recovery unitsto make a larger heat recovery assembly.

FIG. 3 shows a perspective view of a heat recovery unit according to asecond embodiment. The casing 1 contains in this second embodiment twoheat accumulators 5,5', which are placed side by side in each of theirown chambers 40,45. The chambers 40,45 are separated from each other bymeans of a wall 50. The casing 1 has a supply air opening 10, an exhaustair opening 15, an exterior air opening 20 and a used-air opening 25,which each cooperate with the end faces 35 of the heat accumulator 5 and5', respectively. Each of the openings 10-25 is connected to bothchambers 40,45, which means that each opening 10-25 extends from thefirst chamber 40 to the second chamber 45. The supply air opening 10 andthe used-air opening 25 resp. the exhaust air opening 15 and theexterior air opening 20 are separated by means of the wall part 27 resp.28, which can be formed as part of the casing 1.

A fan part 65 which comprises two fans 66,67 (FIG. 4) can be connectedto the supply air opening 10 and the used-air opening 25, and a filterpart 70 which comprises two filters 71, 72 (FIG. 4) can be connected tothe exhaust air opening 15 and the exterior air opening 20.

Precisely as in the heat recovery assembly according to FIG. 2, therotational movements of the heat accumulators 5,5' are so controlledthat when the first heat accumulator 5 is in the first position forexhaust air throughflow, the second heat accumulator 5' is in the secondposition for exterior air throughflow, and vice versa.

Consequently, the ventilation in, for example, a building can beincreased whereby a near enough continuous ventilation of the buildingis achieved. Each of the heat accumulators 5,5' can, as in FIG. 2, beequipped with its own stepping motor 62,62', which brings about therotational movement of each heat accumulator 5,5'. The motors 62,62'shall in this case be synchronized so that when the first heataccumulator 5 is in the first position, the second heat accumulator 5'shall be in the second position and vice versa. This synchronization cantake place by a control unit 60. Alternately, the heat recovery unit canbe equipped with only one motor, where the rotational movement of themotor is transmitted to each of the shafts of the heat accumulators by agear or link mechanism (not shown).

During exhaust air throughflow when the first heat accumulator 5 is setin the first position, air at room temperature in the form of exhaustair flows in through the exhaust air opening 15 and into the firstchamber 40, in which the first heat accumulator 5 is positioned. Theexhaust air flows subsequently through the heat accumulator 5 in adirection which essentially corresponds to the direction of itsthickness. The heat accumulator 5 is thereby heated up by thethroughflowing exhaust air. The air then flows out through the used-airopening 25 in the form of used air och consequently leaves the firstchamber 40. The used air which leaves the user-air opening 25 can thensuitably flow into a channel 82 (FIG. 5), which transports the air outof the building.

At the same time as exhaust air throughflow takes place in the firstchamber 40, exterior air throughflow takes place in the second chamber45, in which the second heat accumulator 5' is set in the secondposition for exterior air throughflow. During exterior air throughflowexterior air flows in through the exterior air opening 20 and into thesecond chamber 45. The exterior air then flows though the second heataccumulator 5' in a direction which essentially coincides with thedirection of its thickness. The exterior air is thereby heated up by thesecond heat accumulator 5' which earlier has been warmed up by exhaustair during exhaust air throughflow. The air then flows out through thesupply air opening 10 in the form of supply air and consequently leavesthe second chamber 45. The supply air which leaves the supply airopening 10 then flows either directly into the building or into a tubesystem which distributes the air to the different rooms in the building(not shown).

According to this embodiment according to FIG. 3, a control means forcontrolling the heat recovery unit can be constructed so that a firstsensor 55 senses the temperature of the exterior air which is flowinginto the exterior air opening 20. The first sensor 55 is connected to acontrol unit 60, and is compensated, which means that it gives signalsto the control unit 60 which signals are the basis for how the heatrecovery unit is to be regulated at different exterior temperatures. Asecond sensor 57 which is placed by the supply air opening 10 andconnected to the control unit 60 senses the temperature of the warmed upsupply air which leaves the supply air openings 10 of the respectivechamber 40,45. This second sensor 57 is regulated, which means that itgives signals to the control unit 60 which signals are a basis for howthe heat recovery unit should be regulated with respect to a suitablyinstalled desired value which is programmed into the control unit. Whenthe supply air temperature is below the desired value of the secondsensor 57, the control unit 60 gives a signal to the respective steppingmotor 62,62', which are connected to the respective shaft 30,30' of theheat accumulators 5,5', whereby the first motor 62 rotates the firstheat accumulator 5 to the second position for exterior air throughflow.At the same time the second stepping motor 62' rotates the second heataccumulator 5' to the first position for exhaust air throughflow.

As an alternative the first sensor 55 senses the temperature of the usedair which leaves the used-air openings 25 of the respective chamber40,45. A reference sensor can, for example, be placed in the buildingwhich is to ventilated, in order to sense the room temperature in thebuilding. The first sensor 55 and the reference sensor are connected tothe control unit 60. The second sensor 57 is placed by the supply airopenings 10 of the respective chamber 40,45 and is connected to thecontrol unit 60, whereby the second sensor 57 senses the temperature ofthe warmed up supply air. When the difference between the temperaturessensed by the first and second sensors 55 resp. 57 and the temperaturesensed by the reference sensor 56 reaches a predetermined value, thecontrol unit 60 gives a signal to the first and second stepping motors62,62', whereby the first motor 62 rotates the first heat accumulator 5to the second position for exterior air throughflow. At the same timethe second stepping motor 62' rotates the second heat accumulator 5' tothe first position for exhaust air throughflow.

FIG. 4 shows a lateral view of a heat recovery unit according to thesecond embodiment. The first heat accumulator 5 is shown with aplurality of parallel lines which extend in the direction of thicknessof the first heat accumulator 5. The parallel lines symbolize that thefirst heat accumulator 5 is built up by a plurality of plates 37. Thesolid arrows show exhaust air flows through the heat recovery assembly.The first heat accumulator 5 is set in the first position for theexhaust air throughflow, wherein exhaust air flows through the exhaustair opening 15 into the first chamber 40, through the first heataccumulator 5 and out through the used-air opening 25 in the form ofused air.

The second heat accumulator 5' is hidden behind the wall 50 whichseparates the first and second chambers 40,45, thus the contours of thesecond heat accumulator are only shown with dashed lines. The secondheat accumulator 5' is set in the second position for exterior airthroughflow which is shown with dashed arrows.

A fan part 65 which comprises two fans 66, 67 is connected to the supplyair opening 10 and the used-air opening 25, and a filter part 70 whichcomprises two filters 71, 72 is connected to the exhaust air opening 15and the exterior air opening 20.

FIG. 5 shows an example of the application of a heat recovery unitaccording to the second embodiment. The heat recovery unit can, forexample, be placed in an isolated place in a building 79. However, it isalso possible to place the heat recovery unit outside the building 79.Exhaust air F in the form of the interior air of the building 79 is ledthrough an exhaust air channel 80 into the filter part 70 of the heatrecovery unit and further in through the exhaust air opening 15 to oneof the two chambers 40 alt. 45, which each contain a heat accumulator5,5'. The exhaust air passes through one of the heat accumulators 5 alt.5' and out through the used-air opening 25 in the form of used air Awhich is led through a used-air channel 82 in order to be let outoutside the building 79. At the same time, exterior air U is led throughan exterior air channel 84 into the filter part 70 of the heat recoveryunit and further in through the exterior air opening 20 to the secondone of the two chambers 40 alt. 45. The exterior air passes through thesecond of the two heat accumulators 5 alt. 5' and out through the supplyair opening 10 in the form of supply air T, which is led through asupply air channel 86 in order to be let into the building 79.

FIG. 6 shows a heat recovery unit according to FIG. 4 where both thefirst and the second heat accumulators 5,5' are in a third position, inwhich position either of the openings 10-25 in the casing 1 of the heatrecovery unit are closed by means of the end faces 35 of the heataccumulators 5,5'. On the other hand, both the exterior openings 20 andthe used-air openings 25 are closed by means of valve leaves 90 whichprevent exterior air to flow from the exterior air opening 20 and theexhaust air opening 25 to the supply air opening 10. In the thirdposition, exhaust air can flow from the exhaust air opening 15 to thesupply air opening 10 without passing through the heat accumulators5,5', whereby an internal air circulation in, for example, a buildingcan be achieved. The third position can be taken during, for example, apower cut or during night or weekend stoppages, when the stepping motorswhich bring about the rotational movement of the heat accumulators 5,5'can be so designed that they automatically rotate the heat accumulators5,5' to the third position during shutdowns.

FIG. 7 shows a lateral view of a heat recovery unit according to a thirdembodiment. The first heat accumulator 5 here is tipped into the secondposition for exterior air throughflow. At the same time the second heataccumulator 5' is topped into the first position for exhaust airthroughflow. Each of the heat accumulators 5,5' is partitioned with adividing wall 95, which extends in the direction of thickness of theheat accumulators 5,5', whereby this dividing wall 95 cooperates withvalve leaves 96, which are synchronized with the rotational movement ofthe associated heat accumulator 5,5'. This synchronization can, forexample, be achieved by means of a link system (not shown). The dividingwall 95 and the valve leaves 96 can together cooperate in order tominimize the losses in the heat recovery when the heat accumulators 5,5'rotate from the first to the second position, and vice versa. Anotherobject of the dividing wall 95 and the valve leaves 96 will be explainedin connection with FIG. 8.

FIG. 8 shows a heat recovery unit according to FIG. 7, where both thefirst and the second heat accumulators 5,5' are in a third position, inwhich position none of the openings 10-25 in the casing 1 of the heatrecovery unit are closed by means of the end faces 35 of the heataccumulators 5,5'. By means of the dividing wall 95 and the valve leaves96, however, two, from each other separated, essentially airtight spacesare formed on each side of the dividing wall 95 and the valve leaves 96.Consequently, exhaust air can flow through the exhaust air opening 15and out through the supply air opening 10, whereby a recycle airfunction in the form of an internal air circulation is achieved in, forexample, a building. As described in connection with FIG. 6, the thirdposition can be taken during, for example, power failures.

In the summer months when the exterior air temperature is relativelyhigh, the accumulator 5,5' in the heat recovery unit can remain ineither the first or the second position for a long time. A time functionbuilt into the control unit 60 can then "exercise" the rotationalfunction at regular time intervals, for example one rotation or tippingper day, whereby the movable parts of the heat recovery unit are broughtinto motion in order to prevent them from sticking.

An advantage of the heat recovery unit according to the invention isthat it can beapplied at a long distance from an outer wall in abuilding, as the air the whole time flows in the same direction in thechannels 80-86 which are connected to the heat recovery unit.

Another advantage of the heat recovery unit is that if the rotatingshaft 30 of the heat accumulator 5,5' is placed horizontally, exhaustair will flow essentially upwards through the heat accumulator 5,'. Thismeans that water which condenses on the heat absorbing surfaces of theheat accumulator 5,' will stay there and in the second position of theaccumulator will be absorbed by the exterior air which flows through theheat accumulator 5,5'. Consequently, no thaw water piping for the heatrecovery unit is required. The efficiency of the heat recovery unit isalso increased in this way because latent heat, which from the beginningis contained in the water vapor, is recovered.

Yet another advantage of the heat recovery unit according to theinvention is that the heat accumulator 5,5,' is easy to clean becausethe throughflow direction of the air though the heat accumulator 5,5'occurs essentially in the direction of its thickness which isconsiderably less than its length and width, so that the throughflowchannels are short och easy to clean by e.g. by rinsing with water.

Yet another advantage of the heat recovery unit according to the presentinvention is that the sound change during the change from the exteriorair throughflow to the exhaust air throughflow and vice versa is verylow. According to the invention, air flows the whole time in the samedirection through the openings 10-25 in the casing 1 and in the channels80-86 which are connected thereto, which means that the sound change islow because no large air volume has to change direction of flow.

Yet another advantage of the heat recovery unit according to the presentinvention is that the pressure drop over the heat accumulator 5,5' islow because the path of the air through the heat accumulator 5,5' isrelatively short. This means that a lower fan capacity is required inorder to produce the flow of the air and it also means a lower soundlevel.

It has been described above how heat can be recovered by the heatrecovery unit according to the invention. It is, however, possible bymeans of the heat recovery unit to shut out warm air from, for example,a building in which the indoor temperature should be less than theoutdoor temperature. The heat recovery unit will then work the other wayround, whereby warm exterior air will give off its heat to the heataccumulator 5 alt. 5' which has been cooled by the exhaust airthroughflow. The exterior air will thus be cooled down and flow into therooms of the building in the form of cool supply air.

I claim:
 1. Heat recovery unit comprising a casing (1) which encloses atleast one regenerative heat accumulator (5), whereby the casing (1) hasa supply air opening (10), an exhaust air opening (15), an exterior airopening (20) and a used-air opening (25), and whereby exhaust air andsupply air alternately pass through the heat accumulator (5),characterized in that the heat accumulator (5), by means of a rotationalmovement, has a valve function which opens and respectively closes saidopenings (10-25) when the heat accumulator (5) rotates from a firstposition for exhaust air throughflow to a second position for exteriorair throughflow, in that the heat accumulator rotates around a shaft(30), and in that the heat accumulator (5), in a direction essentiallyparallel with the shaft (30), has end faces (35), which in the firstposition cover a first pair of said openings (10-25) at the same time asa second pair of said openings (10-25) are open, and in the secondposition cover the second pair of openings (10-25) at the same time asthe first pair of openings (10-25) are open.
 2. Heat recovery unitaccording to claim 1, characterized in that the heat accumulator (5) hasa length, a width and a thickness, of which the thickness isconsiderably less than the length, whereby the exhaust air and supplyair pass through the heat accumulator (5) in the direction of itsthickness.
 3. Heat recovery unit according to claim 2, characterized inthat the shaft (30) extends essentially perpendicular to the directionof the thickness, suitably also perpendicular to a longitudinaldirection.
 4. Heat recovery unit according to claim 1, characterized inthat the first pair of openings (10-25) are made up of the exterior airopening (20) and the supply air opening (10), and that the second pairof openings are made up of the exhaust air opening (15) and the used-airopening (25).
 5. Heat recovery unit according to claim 1, characterizedin that the end faces (35) of the heat accumulator (5) are essentiallyplanar, and that the casing (1) has ends in which the openings (10-25)are positioned which ends are essentially planar.
 6. Heat recovery unitaccording to claim 1, characterized in that the end faces (35) havesealing strips (36) which cooperate with the ends of the casing (1). 7.Heat recovery unit according to claim 1, characterized in that the heataccumulator (5) can be placed in a third position where exhaust air canflow from the exhaust air opening (15) to the supply air opening (10),whereby valve leaves (90) prevent airflow through the exterior airopening (20) and the used-air opening (25).
 8. Heat recovery unitaccording to claim 1, characterized in that the exhaust airflow and aexterior airflow are arranged to flow in opposite directions through theheat accumulator (5).
 9. Heat recovery unit according to claim 2,characterized in that the heat accumulator (5) is divided by means of adividing wall (95) which extends in the direction of the thickness ofthe heat accumulator (5), whereby the dividing wall cooperates withvalve leaves (96) which are synchronized with the rotational movement ofthe heat accumulator (5) in such a way that, when the heat accumulatoris in a third position, two separate essentially airtight spaces areformed on each side of the dividing wall (95) and the valve leaves (96).10. Heat recovery unit according to claim 1, characterized in the afirst sensor (55) is arranged at the used-air opening (25) in order tosense that temperature of used air, that a second sensor (57) isarranged at the supply air opening (10) in order to sense thetemperature of the supply air, and that a reference sensor (56) isarranged in an air volume which is intended to be ventilated, in orderto sense the temperature of the air volume, whereby the first and thesecond sensors (55,57) and the reference sensor (56) each are connectedto a control unit (60) which controls the rotational movement of theheat accumulator (5), based on the temperature which each of the sensors(55-57) senses.
 11. Heat recovery unit according to claim 1,characterized in that the number of heat accumulators (5) is two, thatthe accumulators are placed each in their own chambers (40,45) insidethe casing, that the chambers (40,45) are separated from each other bymeans of a wall (50), that each of the openings (10-25) is connectedwith both chambers, and that the rotational movement of the heataccumulators (5,5') is so controlled that, when the first heataccumulator (5) is in the first position, the second accumulator (5') isin the second position, and vice versa.
 12. Heat recovery unit accordingto claim 1, characterized in that a fan part (65) which comprises twofans (66,67) is connected to the supply air opening (10) and to theused-air opening (25), and that a filter part (70) which comprises twofilters (71,72) is connected to the exhaust air opening (15) and to theexterior air opening (20).
 13. Heat recovery assembly, characterized inthat two heat recovery units according to claim 1 are coupled togetherso that the openings (10-25) of the respective heat recovery unit arejoined to each other, and that the rotational movements of the heataccumulators (5) are so controlled that when the heat accumulator (5) inone of the heat recovery units is in the first position, the other heataccumulator (5') in the second heat recovery unit is in the secondposition, and vice versa.